A pneumatic control valve of this type is known from GB 2 158 534 A. In the case of the said control valve, the plunger piston is of axially very short configuration, and a coaxially extending skirt is screwed on at its end which points into the control valve. The said skirt reaches as far as a cylindrical guide which is a constituent part of a venting plate which is fastened by means of screws to the housing lower part. The plunger piston has a lip seal radially on the outside and is guided in a metallic cap of the control valve with great play in the region of the housing upper part only by means of the lip seal. Accordingly, tilting moments and transverse forces which are caused by the actuation of the plunger piston act directly on the lip seal thereof which, as a result, is subjected to increased wear with impairment of the sealing action. The skirt which is fastened to the plunger piston is guided axially through the first valve piston with great play and in a sealed manner, and does not serve to guide the first valve piston. The first valve piston is guided in the hollow-cylindrical housing upper part in an axial region with radially recessed diameters over a great axial length, the first valve piston being sealed radially on the outside with respect to the inner wall of the housing upper part by two O-ring seals which are spaced apart axially. As a result of this design, no transverse forces and tilting moments act on the first valve piston, but this known pneumatic control valve is comparatively long, since the plunger piston is guided in the cap which is screwed onto the housing upper part. In addition, the recessed bore in the housing upper part, which recessed bore serves as a guide for the first valve piston, requires complicated machining of the said housing upper part.
Against this background, the invention is based on the object of proposing a comparatively short pneumatic control valve which requires a reduced outlay on machining, consists of comparatively few individual parts and is insusceptible to tilting moments and transverse forces which act on the plunger piston of the pneumatic control valve.